Name: _____________________________ ( ) Class: _________ Date: __________

Open the URL http://www1.moe.edu.sg/edsoftware/ir/files/chem-mole/ and complete the worksheet below.

9.3 The Mole (Pg. 131 – 132)• One mole of particles contains ________________________________ particles.

( 6.02 X 1023 is also known as the Avogadro’s constant. )• Symbol of "mole" is __________________________.

• Definition of mole:

A mole is the _____________________________________________________________

(atoms, molecules or ions) as the number of atoms in 12 g of carbon-12

• ____ mole of water molecules is made up of _____ moles of hydrogen atoms and

____ mole of oxygen atoms.

• Conversion between number of moles and number of particles:

Number of particles

Number of moles = 6 X 1023

The Molar Mass

• The __________________________________________________________________

is known as its molar mass.

• The unit for molar mass is ________________________________________ (g/ mol).

• Molar mass of an element = Relative atomic mass (Ar) of the element in grams.

Mass of element (g)

Number of moles of an element = Relative atomic mass of the

element

Mass of compound (g)

Number of moles of a compound = Relative molecular mass

Mass of compound (g)

= Relative formula mass

Secondary 3 Express Chemistry (with SPA)Chapter 9: The MoleNotes (Mole and Molar Masses)

Practice Questions

1. How many moles of atoms are there in (a) 2.4 X 1024 atoms of sodium?

No. of moles of sodium atoms =

=

= _______________ mol

(b) 1X 1023 atoms of argon gas?

No. of moles of argon atoms =

= _______________ mol

2. How many(a) atoms are there in 0.5 mol of lead?

No. of lead atoms = No. of moles X Avogadro’s constant

= 0.5 X 6 X 1023

= ___________________________

(b) atoms are there in 2 moles of chlorine (Cl2) gas? (*Hint Refer to Example 3 on Page 132)

(c) water molecules are there in 36g of water molecules?

4

No. of sodium atomsAvogadro’s constant

2.4 X 10 24 6 X 1023

_________________

Note: Such shorts statements are needed in solving questions on

moles.

3. Calculate the mass of:(a) 4 moles of phosphorous atoms:

(b) 3 moles of oxygen molecules, O2

(c) 2 moles of magnesium chloride, MgCl2

(d) 1.5 X 1023 carbon atoms:

4. How many moles of (a) potassium atoms are contained in 8g of potassium atoms?

(b) calcium carbonate are contained in 20g of calcium carbonate (CaCO3)?

(c) oxygen atoms are contained in 64g of sulphur dioxide molecules?

4What are some problems faced when doing the questions?

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